Coil question

sseres

sseres

XS650 Junkie
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Re tci coil... If I see a spark when I ground a plug to the engine block, does that mean that I have to have a good coil? Can I see a spark but be in a situation where it's not if enough?

I've replaced spark plugs and not gotten to the bottom of a "won't start" mystery, and after cleaning carbs, replacing battery, and cleaning and wiggling every stupid thing I can think. The only thing I don't really know how to do is tell if the coil is ok.... Or can I?
 
You need four things for your engine to run. Fuel, Spark, Compression and proper timing for all these events. Each event has to be verified and tested.
Are the spark plugs wet with fuel after cranking? If not spray some raw fuel or starting fluid through the carbs while cranking over.
Did you do a compression check of each cylinder? If compression is low, less than 100 PSI, you must do a leak down test to verify the cause of the low compression.
As far as spark goes, must be a fat, bright blue spark. Cam/valve timing should be inspected. An inline spark tester may be helpful in troubleshooting. A weak spark could be a problem. I would read up on TCI unit problems on this forum before suspecting a coil that is providing some spark.
Do some checking and post your results!
 
thanks for the pep talk. I think I'm just getting frustrated. Newly rebuilt engine so I didn't dare think I suddenly didn't have compression (and it sounds like it's work for the starter, and it's not easy to use the kick start) but I'll definitely check that next time I'm out there. Plugs are definitely wet (actually thought it was flooding so that's I took the carbs all apart). With the TCI, other than having had the cam lined up when I put her back together, I wasn't aware there were any timing issues I had to fart with.

So, that's what led me back to the coil. I see they're like $30 from Mikes, and most people in the forum say the only way to test the iggy is to swap it.

Oh, and then there was gas all over when I went out to close the garage last night leaking slowly from one of the carb bowl drains and then from somewhere higher up. I may have broke a fuel line or something. :banghead:

Calgon, take me away!
 
A yellow spark is considered weak and a nice blue spark strong.
It is easier to detect in the dark so maybe a sheet, black trash bag or simliar covering may help.
The electric leg does rob the system of fire power so if you could kick it, you might be ahead.
You list petcocks in your signature. The manuals shouldn't let gas pass in the off position. I've had problems catching the wavy ring under the faceplate causing a weep.
 
yes, so I was having an extra awesome plate full of brainless yesterday and didn't think to turn the petcocks off until I found the leak hours later. They really do a good job of keeping gas in the tank, but, apparently do have to be off :)
 
sseres said:
so, say I get one of these to see if my coil is bad. How do I know which lead goes to each side of the motor?

https://www.mikesxs.net/product/17-6803.html
Click to expand...

It does not matter................TCI/coil sends a spark every time the pistons come to the top of their stroke. One cylinder fires and the other does not fire because its on the exhaust stroke.

As to your "no start", have you confirmed that the fuel supply orifice, for the choke circuit, is clear....................its in the bottom of the float bowl. Cold starts need the choke to be working.
 
retiredgentleman said:
It does not matter................TCI/coil sends a spark every time the pistons come to the top of their stroke. One cylinder fires and the other does not fire because its on the exhaust stroke.
Click to expand...

wo... just to clarify, so even though one side is on exhaust cycle, both spark plugs fire?



as for the choke thingy, I think i'm good. I took the carbs off and went through them with cleaner and checked everything before putting them back on. I'm pretty sure I'm getting choke... i think.
 
Yes, both plugs fire each time the pistons reach (near) TDC. One cylinder will be at TDC on the compression stroke and that's the one that will fire. The other will be on TDC of it's exhaust stroke and that spark will be what's called a "waste spark", obviously because it's wasted and doesn't fire anything. There is no fresh gas/air charge in that cylinder to fire at that time. It's just completing it's exhaust stroke, pushing the spent gases out.

To check and see if your choke jets are clear, you'll need to do this. If they're plugged, the choke won't function .....

ChokeJet2.jpg
 
Another thought.... if your plugs are wet when you pull them, you may be flooding... try cranking it over with the throttle held open, without choke, so that the cylinder gets some air.

Your problem with gas leaking while petcock is "on", and wet plugs, leads me to think it may be a carb problem (like a sticking float valve) and letting in WAY too much gas.

Next time you pull the plugs and they are wet, take a propane torch and heat them up (yes, they can stand a lot of heat!) so that they are good and hot and dry, reinstall them then crank it over without the choke and holding the throttle open!

:thumbsup:

If you are not sure if you're getting choke, try shooting in a spritz of starting fluid, that will sort out any lack-of-gas: if it fires and tries to start, it isn't getting enough fuel. But it still sounds to me like you are getting too much fuel....
 
+1 to what bpeckm posted. I was also thinking that if the petcocks are on and gas is leaking, then there is a problem with carbs (float height?)
Honestly, it doesn't sound to me like this is a spark problem.

Are you sure cam timing is correct after rebuild?

Have you verified valve clearances?
 
There are ways to test a coil without substitution. Ohm checks work well. On your TCI bike the primary side should read 2.25 to 2.75 ohms with infinity to ground. On the secondary side it should be 10,500 to 15,500 ohms, infinity to ground. Clymer book page 181 tells how, pic on page 184.
Leo
 
for lack of smarts (laziness? frustration?), I didn't really do any good diligent checking of the ohms on the coil i have.

and, I guess I have to clarify the gas leak, because I don't think it's a float level thing -- the only time gas comes pouring out of my bike has been the times (yes, unfortunately... times) I've dumped it over. Not to say it can't be a float issue, but my guess is that I have a situation where I think I'm more flooded than dry. My thought is that if the gas isn't being burned up but a spark, it just gets wetter and wetter.

But getting back to the best advice on the forum about troubleshooting ('what was the last thing you did before things stopped working?'), I'm perplexed. I was working on the starter gears with both LH and RH covers off. Had get it all buttoned back up and THAT's when all this silliness started. The starter is definitely working the way it's supposed to. I'm getting that anemic spark, but rarely hear anything other than maybe a 1x fire at best. otherwise just kachooga kachooga kachooga.

The bike did fall over once when I was trying to fuss it around on the lift table (no, I'm not proud)... could I have fratzed something somehow that way? Nothing looks broken.

Someone above asked about timing. With the TCI set up, as far as I know, as long as I got the cam lined up with the timing mark on the rotor, I'm good to go... so, I don't think it's a timing issue.
 
XSLeo said:
There are ways to test a coil without substitution. Ohm checks work well.
Click to expand...

Each coil I had that failed (two of them) measured fine. There was a high voltage breakdown in the secondary winding that would not show up on a meter testing using a low voltage.

Symptom is hard starting, fouling plugs, and all that, you know. Eventual or immediate no-run, cured by a new coil, but the old coil measured fine.

Get the critical things right and the bike will start easily and run. Good battery, working choke, good TCI, good pickup coil, good ignition coil, good connectiions.

In order of likelyhood of being bad - connections including switches fuses and p.o. weirdness, battery, coil, pickup coil, choke, TCI. Needs good compression it goes without saying.



P.S. Have basically a spare igntion system handy, coil, TCI, pickup, ready to put on or test by substitution. You can check the pickup coil reliably with a meter, but have one in case you need one. I did :)

I also had a plug wire that vibrated out of the coil. The plug wire compressed to the point where the little rubber collar didn';t hold it very well and it came almost out of the coil. Wasn't making good contact with the coil and the bike would stall and not start, got worse and worse. But never left me stranded away from camp before I traced it down and fixed it. Good ol' Trigger.

There was also a split screw down cap at the coil on that wire. Save your old caps for spares. Could have fixed the old cap temporarily by putting a plastic wire tie around it tightly.
 
Last edited:
That type of coil just uses a bare plug wire with no crimp on it. If you look into the plug wire holes on the coil, you'll see what appears to be the end of a wood screw sticking out of each one. You simply "screw" the wire onto that. Have the screw-on end cap and rubber dounut on the wire first. Then, once the wire is screwed in, slide the dounut up snug to the coil and screw the cap on tight. The cap compresses the dounut onto the wire which seals and helps hold it into the coil. I do this to my wire ends before screwing them in, also brush a little dielectric grease on them .....

PlugWireEnd.jpg
 
sseres, when checking spark are you using the starter? If so, it draws so much current from the battery the voltage drops to so low a value the coil doesn't get enough to spark well.
Try hooking up a jumper battery with jumper cables to your battery then try it.
I have a small car battery and a good set of cables I use for such things. Often if a bike battery starts to get weak, using the spare battery to just crank the starter, the bike battery just for ignition I can get the bike to start for the first start of the day.
To do this I hook up the cables from the spare battery, the other end the black to a good frame ground, the foot peg mount nut works very well. Put a large screwdriver in the red cable clamp, with the rubber cover off the cable to the starter at the starter relay, touch the screwdriver to the stud. This sends the power from the car battery straight to the starter.
This way the bike battery only powers the ignition.
On the bike I had this problem with was the 75 with the 750 kit installed. It cranked a bit hard first thing in the morning. I replaced the battery with an 8 cell Ballistic Battery I replaced the battery cables, hot and ground, as well as to the starter with 4 ga cables. I also ran a 4 ga cable from one of the starter mount bolts to battery negitive.
This way I have a 4 ga cable carrying all the current the starter needs as straight as I can. No frame to engine or frame to battery connections to worry about.
The new battery has 275 CCA's, the stocker is rated about 200 CCA's. This extra power and cables that can better handle the current don't draw the voltage below what it takes to coil to fire the plugs.
Be sure your battery is fully charged and test with the kick start.
Leo
 
ok, update.

So far I've:
a) checked electrical connections
b) got a new battery (closed cell) and have kept it on the trickle charger
c) took off carbs, went through them, found no issues but sprayed out all the little ports anyway. New float gaskets, new bowl plugs.
d) took off RH cover, mostly because it was leaking and I couldn't figure out why. Turns out two things were wrong -- 1)e the dumb thing wasn't flat along the bottom edge which is what I figure was the reasons for the leak. 2) the tach gear wouldn't turn!! It was stuck and I had no idea why or how that happened because I had it all apart when I was doing the engine and it certainly wasn't stuck then. Not sure if that was enough to keep my poor engine from turning over. So, I got a different RH cover with a working tachy gear, made sure the cover was straight this time, and installed it with a new RH cover gasket.
e) replaced the coil with the black one from Mikes.
f) new spark plugs
g) cranked after each step and basically the same symptom: cachigga cachigga cachigga then it cranked!!! Well, just for a second. And that was it. I turned the throttle open and it sped up but cut at top speed. So then more cachigga cachigga backfire cachigga cachigga. Not really able to get it started with a kick either. Walked away, let battery charge, but same thing tonight. cachigga cachigga backfire cachigga.

Today at lunch I got this from HF:
http://www.harborfreight.com/10-2-55-amp-6-12-volt-battery-charger-engine-starter-66783.html?ccdenc=eyJjb2RlIjoiNzY5MTc2NjIiLCJza3UiOiI2Njc4MyIsImlzIjoiMzIuOTkiLCJwcm9kdWN0X2lk%0D%0AIjoiMTk4NiJ9%0D%0A
with the idea that I'm just not getting enough cranking amps. didn't get a chance to try this out yet.

I find myself wondering if there's not something wrong with the TCI box, although it was working fine before all this dumb stuff started.e

This has GOT to be something stupid I'm not thinking of, right?
 

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